Initial commit: read flac metadata.

lib/flac/flac.go

@@ -0,0 +1,63 @@
+package flac
+
+import (
+	"bytes"
+	"fmt"
+	"os/exec"
+	"strconv"
+)
+
+type Metadata struct {
+	SampleRate int64
+	BPS        int64
+	Channels   int64
+	NumSamples int64 // Total length of file in samples (per channel).
+}
+
+func GetMetadata(path string) (md Metadata, err error) {
+	cmd := exec.Command(
+		"metaflac",
+		"--show-sample-rate",
+		"--show-bps",
+		"--show-channels",
+		"--show-total-samples",
+		path)
+
+	out, err := cmd.Output()
+	if err != nil {
+		return md, fmt.Errorf("Failed to open file: %w", err)
+	}
+
+	l := bytes.Split(out, []byte{'\n'})
+	if len(l) != 5 {
+		return md, fmt.Errorf("Output not understood:\n%s", out)
+	}
+	l = l[:4]
+
+	md.SampleRate, err = strconv.ParseInt(string(l[0]), 10, 64)
+	if err != nil {
+		return md, fmt.Errorf("Invalid sample rate: %w", err)
+	}
+
+	md.BPS, err = strconv.ParseInt(string(l[1]), 10, 64)
+	if err != nil {
+		return md, fmt.Errorf("Invalid bps: %w", err)
+	}
+
+	md.Channels, err = strconv.ParseInt(string(l[2]), 10, 64)
+	if err != nil {
+		return md, fmt.Errorf("Invalid channels: %w", err)
+	}
+
+	md.NumSamples, err = strconv.ParseInt(string(l[3]), 10, 64)
+	if err != nil {
+		return md, fmt.Errorf("Invalid length: %w", err)
+	}
+
+	return md, nil
+}
+
+func Load(path string, nSamples int64) (L []float32, R []float32, err error) {
+	// TODO!
+	return
+}

lib/flac/flac_test.go

@@ -0,0 +1,14 @@
+package flac
+
+import (
+	"log"
+	"testing"
+)
+
+func TestGetMetadata(t *testing.T) {
+	md, err := GetMetadata("test_files/audio.flac")
+	if err != nil {
+		t.Fatal(err)
+	}
+	log.Printf("%v", md)
+}